Question

write p for physical change or c for chemical change.
7.1) a change causes matter to look different but does not change the matter itself.
7.2) bubbles are made.
7.3) a change creates a different type of matter with new properties.
7.4) a pencil breaks in half.
7.5) water evaporates into steam.
7.6) a pencil is burned in a fire.
7.7) a banana rots.
7.8) a car becomes rusty.
7.9) matter changes states.
7.10) most mixtures are made by this type of change.
7.11) this change is never undone.
7.12) light and heat are produced.
7.13) a fruit is cut to look like a shark.
7.14) a fruit rots.
write the correct answers.
7.15) when sugar dissolves in water, it is a physical change. why is it a physical change?
7.16) why is milk spoiling a chemical change?

Explanation:

• 7.1 A physical change (\(P\)) causes matter to look different but doesn't change the matter itself.
• 7.2 Bubbles in a chemical reaction (\(C\)) often indicate gas formation from a new substance.
• 7.3 A chemical change (\(C\)) creates new - matter with new properties.
• 7.4 A pencil breaking (\(P\)) is a physical change (shape alteration, no new substance).
• 7.5 Water evaporation (\(P\)) is a physical state - change (liquid to gas, same \(H_2O\) molecules).
• 7.6 Burning a pencil (\(C\)) is a chemical change (wood reacts with oxygen, new substances like ash and \(CO_2\)).
• 7.7 Banana rotting (\(C\)) is a chemical change (microbial action creates new substances).
• 7.8 Car rusting (\(C\)) (iron reacts with oxygen and moisture, new substance - rust (\(Fe_2O_3\cdot xH_2O\))).
• 7.9 Matter changing states (\(P\)) (e.g., melting, freezing - physical changes).
• 7.10 Most mixtures (\(P\)) (e.g., sand and water - no new substance formed).
• 7.11 Chemical change (\(C\)) (new substances formed, often irreversible).
• 7.12 Light and heat (\(C\)) (e.g., combustion - chemical reaction).
• 7.13 Cutting fruit (\(P\)) (shape change, no new substance).
• 7.14 Fruit rotting (\(C\)) (microbial - induced chemical change).
• 7.15 Sugar dissolving (\(P\)): No new substance. Sugar (\(C_{12}H_{22}O_{11}\)) molecules disperse in water. Can recover sugar via evaporation.
• 7.16 Milk spoiling (\(C\)): Microbes metabolize lactose etc. New substances (e.g., lactic acid) with different taste, smell.

Answer:

7.1 \(P\)
7.2 \(C\)
7.3 \(C\)
7.4 \(P\)
7.5 \(P\)
7.6 \(C\)
7.7 \(C\)
7.8 \(C\)
7.9 \(P\)
7.10 \(P\)
7.11 \(C\)
7.12 \(C\)
7.13 \(P\)
7.14 \(C\)
7.15 Sugar dissolves in water is a physical change because no new substance is formed. Sugar molecules disperse in water and can be recovered by evaporation.
7.16 Milk spoiling is a chemical change because microbes cause chemical reactions, forming new substances (e.g., lactic acid) with different properties (taste, smell).